package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CacheClient {

    //自定义线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }


    /*
     * 将任意类型的java对象序列化为json字符串，并保存到string类型的key中
     * */
    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }


    /*
     * 将任意类型的java对象序列化为json字符串，并保存到string类型的key中并设置逻辑过期时间用于解决缓存击穿
     * */
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));

        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }


    public <R, ID> R queryWithPassThrough(String keyPre, ID id, Class<R> type, Long time, TimeUnit unit, Function<ID, R> dbFallback) {
        String key = keyPre + id;

        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {//null "" 都是false
            //3.存在,直接返回
            //根据json字符串获取对象
            return JSONUtil.toBean(json, type);
        }

        //判断命中的是否是空值
        if (json != null) {//从上面下来只有两种情况null 或者""
            //空值的话返回错误信息
            return null;
        }


        //4.不存在,根据id查询数据库,自己不知道逻辑要别人传递
        R r = dbFallback.apply(id);
        //5.数据库不存在,返回错误
        if (r == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", time, unit);
            return null;
        }
        //6.存在,写入redis,设置超时时间.超时剔除策略
        set(key, r, time, unit);
        //7.返回
        return r;
    }


    /*
     *利用逻辑过期来解决缓存击穿
     * */
    public <R, ID> R queryWithLogicalExpire(String keyPre, ID id, Class<R> type, Long time, TimeUnit unit, Function<ID, R> dbFallback) {
        String key = keyPre + id;

        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if (StrUtil.isBlank(json)) {//null "" 都是false
            //未命中返回
            return null;
        }

        //4.命中,将json反序列化
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期,直接返回
            return r;
        }

        //5.2过期则缓存重建
        //6.缓存重建,
        //6.1获取互斥锁
        String lock = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lock);

        if (isLock) {
            //6.2成功,开启独立线程来缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //缓存重建
                    //1.查数据库
                    R r1 = dbFallback.apply(id);
                    //2.写入redis
                    setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unLock(lock);
                }
            });

        }

        //6.3返回商铺信息
        return r;
    }


    /*
     * 获取锁
     * */
    private boolean tryLock(String key) {
        Boolean aBoolean = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", LOCK_SHOP_TTL, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(aBoolean);
    }


    /*
     * 删除锁
     * */
    private void unLock(String key) {
        stringRedisTemplate.delete(key);
    }

}
